This invention relates to newly identified polynucleotides, polypeptides encoded by such polynucleotides, the use of such polynucleotides and polypeptides, as well as the production of such polynucleotides and polypeptides. More particularly, the polypeptide of the present invention is a human amine transporter. The invention also relates to inhibiting the action of such polypeptides.
Neurosensory and neuromotor functions are carried out by neurotransmission. Neurotransmission is the conductance of a nerve impulse from one neuron, called the presynaptic neuron, to another neuron, called the postsynaptic neuron, across the synaptic cleft. Transmission of the nerve impulse across the synaptic cleft involves the secretion of neurotransmitter substances. The neurotransmitter is packaged into vesicles in the presynaptic neuron and released into the synaptic cleft to find its receptor at the postsynaptic neuron. Transmission of the nerve impulse is normally transient.
An essential property of synaptic transmission is the rapid termination of action following neurotransmitter release. For many neurotransmitters, including catecholamine, serotonin, and certain amino acids (e.g., gamma-aminobutyric acid (GABA), glutamate and glycine), rapid termination of synaptic action is achieved by the uptake of the neurotransmitter into the presynaptic terminal and surrounding glial cells. This rapid re-accumulation of a neurotransmitter is the result of re-uptake by the presynaptic terminals.
At presynaptic terminals, the various molecular structures for re-uptake are highly specific for such neurotransmitters as choline and the biogenic amines (low molecular weight neurotransmitter substances such as dopamine, norepinephrine, epinephrine, serotonin and histamine). These molecular apparatuses are termed transporters. These transporters move neurotransmitter substances from the synaptic cleft back across the cell membrane of the presynaptic neuron into the cytoplasm of the presynaptic terminus and therefore terminate the function of these substances. Inhibition or stimulation of neurotransmitter uptake provides a means for modulating the effects of the endogenous neurotransmitters.
Re-uptake of neurotransmitter substances by the transporters may be sodium-dependent. For instance, the GABA transporter is a member of the recently described sodium-dependent neurotransmitter transporter gene family. These transporters are transmembrane receptor complexes having an extracellular portion, a transmembrane portion and an intracellular portion. A significant degree of homology exists in the transmembrane domains of the entire family of sodium-dependent neurotransmitter transporter proteins, with considerable stretches of identical amino acids, while much less homology is apparent in the intracellular and extracellular loops connecting these domains. The extracellular loop in particular seems to be unique for each transporter. This region may contribute to substrate and/or inhibitor specificities.
Identifying the novel amine transporter of the present invention and elucidating the structural and functional distinctions between different types of transporters is important in understanding the cellular and molecular bases of behavior and disease.
The polypeptide of the present invention has been putatively identified as an amine transporter. This identification has been made as a result of amino acid sequence homology to the rat amine transporter.
In accordance with one aspect of the present invention, there is provided a novel mature polypeptide which is a human amine transporter, as well as biologically active and diagnostically or therapeutically useful fragments, analogs and derivatives thereof.
In accordance with another aspect of the present invention, there are provided isolated nucleic acid molecules encoding a human amine transporter, including mRNAs, DNAs, cDNAs, genomic DNAs as well as analogs and biologically active and diagnostically or therapeutically useful fragments and derivatives thereof.
In accordance with yet a further aspect of the present invention, there is provided a process for producing such polypeptide by recombinant techniques comprising culturing recombinant prokaryotic and/or eukaryotic host cells, containing a human amine transporter nucleic acid sequence, under conditions promoting expression of said protein and subsequent recovery of said protein.
In accordance with yet a further aspect of the present invention, there is provided a process for utilizing such polypeptide, or polynucleotide encoding such polypeptide for screening for agonists and antagonists and ligands to such polypeptide.
In accordance with yet a further aspect of the present invention, there is provided a method for utilizing such agonists for stimulating the amine transporter uptake of neurotransmitter ligands for the treatment of diseases related to under-expression of the amine transporter or over-expression of the ligand.
In accordance with yet another aspect of the present invention, there is also provided a process for using antagonists for inhibiting the amine transporter uptake of neurotransmitter ligands for the treatment of diseases related to over-expression of the amine transporter or under-expression of the ligand.
In accordance with yet a further aspect of the present invention, there are provided antibodies against such polypeptides.
In accordance with yet a further aspect of the present invention, there are also provided nucleic acid probes comprising nucleic acid molecules of sufficient length to specifically hybridize to human amine transporter sequences.
In accordance with still another aspect of the present invention, there are provided diagnostic assays for detecting diseases related to the under-expression and over-expression of the amine transporter polypeptide and mutations in the nucleic acid sequences encoding such polypeptide.
In accordance with yet a further aspect of the present invention, there is provided a process for utilizing such polypeptides, or polynucleotides encoding such polypeptides, for in vitro purposes related to scientific research, synthesis of DNA and manufacture of DNA vectors.
These and other aspects of the present invention should be apparent to those skilled in the art from the teachings herein.